This invention relates to sewing machine work supporting frame construction, and more particularly to reinforcing means for a molded sewing machine frame designed with an unobstructed channel for accommodation of a preassembled operative mechanism module.
It was conventional in sewing machine frame construction to provide for numerous machining operations after the initial molding or casting of the frame so as to provide for insertion, clearances and support of the various elements of the operating mechanism one by one into the frame. As a result, in conventional sewing machine frame construction, practically unlimited choice was available for the location of integral reinforcing webs, partitions, ribs and the like. Because of the freedom which conventional frame construction provided as to the number and location of integral reinforcing segments, no serious problems arose in preventing objectionable deformation in response to the forces to which the frame was subjected during sewing operation.
With the quest for cost effectiveness in the manufacture and assembly of sewing machines, however, the technique of preassembling sewing machine operating mechanism into modules for insertion bodily into the sewing machine casing is increasingly being utilized. Such modular construction affords double cost savings; i.e., not only is it easier to assemble individual parts into a module than into the often poorly accessible areas within a sewing machine casing, but the number and complexity of machining operations on the sewing machine casing may be reduced. A problem which arises however, is that because clear openings or channels are required to be provided in the sewing machine frame for introduction and accommodation of the preassembled modules of operating mechanism, freedom of location of integral reinforcing ribs and the like is sacrificed.
The U.S. Pat. No. 4,193,361, Mar. 18, 1980, discloses one approach to the solution of this problem. By providing a sewing machine bed construction which is open to the side, somewhat greater freedom is provided in choice of the size and location of the ribs, webs, etc., which are integral parts of the casing. In this referenced patent, the cover is not provided with any particular form for reinforcing purposes and in fact, the cover is not included in the illustrations.